1. Field of the Invention
The present invention relates to a thin film magnetic head employed in a magnetic recording/reproduction apparatus such as a magnetic disk apparatus, and a manufacturing method thereof.
2. Discussion of Background
In order to assure high density recording in magnetic disk apparatuses, the recording track width of thin film magnetic heads has been reduced to 1.0 .mu.m or less in recent years. One of the prior art methods to achieve such a small recording track width is to machine the air bearing surface (ABS) of the slider. Indented portions having a specific depth are obtained by polishing the surface of the slider facing opposite the medium, defining a pattern by removing the area that contains the end surface of the magnetic film through the Focused Ion Beam (FIB) etching technique or through photolithography, and machining the air bearing surface in conformance with the pattern thus defined by employing a means such as ion milling.
IEEE Transactions on Magnetics Vol. 27, No. 6, November 1991, for instance, discloses a reduced track width obtained by applying the FIB etching technique on the ABS of the slider, and IEEE Transactions on Magnetics Vol. 30, No. 6, November 1994 discloses a thin film magnetic head having a reduced track width obtained by machining the slider through photolithography.
During the machining processes described above, the end surface of the magnetic film constituting the pole tip becomes exposed within the indented portions. As a means for protecting this end surface from oxidation or corrosion, a single protective film is formed over the entire surface facing opposite the medium including the ABS and the indented portions. Normally, the protective film is constituted of diamond-like carbon (DLC).
However, since the protective film has a consistent thickness and is formed onto the ABS as well as inside the indented portions, this structure poses a problem in that in order to cover the entire end surface of the magnetic film exposed within the indented portions, it is necessary to use a rather thick protective film. This means that the protective film formed onto the air bearing surface is thick as well, causing spacing loss which in turn leads to deteriorated electromagnetic conversion characteristics.
The problem described above occurs whenever an area containing a pole tip is removed and thus, it is not limited to the process performed to achieve a reduction in the track width.